1. Field of the Invention
This invention relates generally to mixers, and more particularly to an apparatus for mixing particulate materials such as silage, meal, concentrates, grains, hay, and the like.
2. Information Disclosure Statement
Mixing devices are commonly used to mix animal feedstuffs prior to distribution at a feedlot. The feedstuffs may comprise various quantities of particulate materials which must be uniformly mixed to ensure uniform intake by the animals. The blending and mixing operation may take place at a central location from which the mixed material is distributed, but often the various ingredients are placed in a mobile mixing truck box or trailer and mixed enroute to final distribution.
An early apparatus for mixing animal feeds is shown in Haines U.S. Pat. No. 1,769,576. Material to be mixed is circulated by conveyor to a hopper in which rotating toothed rollers break up lumps and mix the feed material.
In Wolfe U.S. Pat. No. 2,676,002, feed materials are mixed in a wagon box just prior to discharge by two rotating mixing/beating elements, one above the other.
Copeland et al U.S. Pat. No. 3,090,605 discloses a feed mixer within a hopper apparatus for mixing animal feeds passing to an area of use or storage. Two fixedly mounted screws rotate to move material to one end of the hopper, while a third, lower screw rotates to move the material in the opposite direction and to exit via the hopper.
Similarly, the mixer in the feed wagon of Carter et al U.S. Pat. No. 3,995,836 comprises a plurality of fixed-position augers which move the material to be mixed in opposite directions.
Buschbom et al U.S. Pat. No. 4,462,693 shows a mixing box having two fixed lower augers and two fixed upper paddle conveyors. The paddle conveyors move particulate materials in a direction opposite that of the lower augers.
Neier U.S. Pat. No. 3,790,138 shows a mixing apparatus with two augers fixedly mounted in the lower portion of the wagon box to move material in opposing directions. Paddle agitators are located in the upper portion of the box. The auger flights are arranged to provide an area of mutual convergence adjacent a discharge opening. One drawback of such auger arrangement is that hay becomes wedged between the box wall and augers, exerting a destructive force on the drive mechanisms.
An agitator which turns on a longitudinal axis in a space comprising substantially the whole of the trailer body is shown in Walley U.S. Pat. No. 4,298,289. This large agitator sweeps material upward to a smaller secondary agitator on which are randomly arranged spines. The trailer box is emptied by discharge from an opening beneath the secondary agitation. Trailer contents are mixed by rotational tumbling rather than axial transfer. As a result, end-to-end mixing is extremely limited.
Crose U.S. Pat. No. 3,672,640 discloses a similar paddle-wheel type mixer except that the shaft of the main agitator supports one or more helical ribs to form an auger. As a fixed part of the main agitator assembly, the auger rotational speed is limited to that of the main agitator, severely reducing end-to-end mixing. In Crose, the secondary agitator comprises an auger for axial movement of the particulate materials in a side chamber and discharge therefrom.
Another feed mixer similar in configuration to the Walley and Crose patents is shown in Neier et al U.S. Pat. No. 4,506,990. The primary agitator or large rotor is of paddle wheel type construction with both fixed rotor bars and bars with spring-mounted wiper blades. A pair of secondary augers with opposing screw pitch are located in an auxiliary chamber having a discharge gate. End-to-end mixing depends upon spill-over of materials from the auxiliary chamber into the main chamber.